By 2010, the most recent year for which EIA has global data, U.S. emissions fell to 5.6 billion metric tons, while global emissions rose to 31.8 billion metric tons. Accordingly, the United States accounted for just 18 percent of global carbon dioxide emissions in 2010.

The first-quarter 2012 U.S. emissions numbers indicate the U.S. share will likely fall further to 15 percent of global emissions this year.

Chinese Emissions Growing

The 2010 numbers show China emitted more carbon dioxide than the entire Western Hemisphere. Chinese emissions approximately tripled between 2000 and 2010, while U.S. emissions declined. Preliminary data indicate Chinese emissions continued their steep rise between 2010 and 2012, while U.S. and Western Hemisphere emissions continued to decline.

China accounted for 12 percent of global carbon dioxide emissions in 2000, but that rose to 26 percent in 2010.